The present invention generally pertains to compressors used to compress fluid. More particularly, embodiments of the present invention relate to a high-efficiency centrifugal compressor assembly, and components thereof, for use in a refrigeration system. An embodiment of the compressor assembly incorporates an integrated fluid flow conditioning assembly, fluid compressor elements, and a permanent magnet motor controlled by a variable speed drive.
Refrigeration systems typically incorporate a refrigeration loop to provide chilled water for cooling a designated building space. A typical refrigeration loop includes a compressor to compress refrigerant gas, a condenser to condense the compressed refrigerant to a liquid, and an evaporator that utilizes the liquid refrigerant to cool water. The chilled water is then piped to the space to be cooled.
One such refrigeration or air conditioning system uses at least one centrifugal compressor and is referred to as a centrifugal chiller. Centrifugal compression involves the purely rotational motion of only a few mechanical parts. A single centrifugal compressor chiller, sometimes called a simplex chiller, typically range in size from 100 to above 2,000 tons of refrigeration. Typically, the reliability of centrifugal chillers is high, and the maintenance requirements are low.
Centrifugal chillers consume significant energy resources in commercial and other high cooling and/or heating demand facilities. Such chillers can have operating lives of upwards of thirty years or more in some cases.
Centrifugal chillers provide certain advantages and efficiencies when used in a building, city district (e.g. multiple buildings) or college campus, for example. Such chillers are useful over a wide range of temperature applications including Middle East conditions. At lower refrigeration capacities, screw, scroll or reciprocating-type compressors are most often used in, for example, water-based chiller applications.
In prior simplex chiller systems in the range of about 100 tons to above 2000 tons, compressor assemblies have been typically gear driven by an induction motor. The components of the chiller system were designed separately, typically optimized, for given application conditions, which neglects cumulative benefits that can be gained by fluid control upstream in between and downstream of compressor stages. Further, the first stage of a prior multistage compressor used in chiller systems was sized to perform optimally, while the second (or later) stage was allowed to perform less than optimally.